nozzle filament output temperature

It occurred to me before, an aluminium block with a thermistor or thermocouple pushed into a hole a few mm from the thread. Often with an airgap not close to the nozzle tip.
Given potential lag trying to maintain a set temperature. especially with air attempting to cool the extrusion and nozzle. which can lead to premature hardening of pla
causing weaker layer bonding.

There is a video somewhere on youtube, where they had kapton tape attaching a thermistor direct to the nozzle. anyone ever try it? what are the pros & cons.
Digital Laser Infrared Thermometers are not overly expensive. How difficult would it be to hack one to use instead of conventional temp sensors.
Pointed at the tip the extrusion temperature would be more accurate.

It always falls or is knocked off.... causing the hot end to keep heating and eventually fire.
Less of an issue with modern firmware that notices its putting more and more power in the hot end that isn't heating up and will stop.

The difference between filament temp in nozzle
and the temp at the thermistor is miniscule.

The A to D (analog to digital) conversion is probably less precise!

If you really needed to know you could compute
temp effect between :
filament and brass nozzle
Brass nozzle to aluminum block
Al block to material around thermistor
material around thermistor to thermistor

Non contact IR themometers have too large a
measurement area and are dependent on reflectivity of material

So you using a filament material that you
must control temp +- 0.0001 deg C?

Could use:Infrared sensor of the thermoMETER CTLaser series are used for precise, industrial measurements. Using two laser beams, the measurement spot is marked which ensures a precise temperature measurement. thermoMETER CTLaser temperature sensors are used in numerous applications. From extremely low temperatures (-50°C) to the highest temperatures (2200°C), these IR sensors measure precisely and reliably.
but minimum spot size 0.9mm +- 1% deg C and about $10000

Good Luck

BTY a small alligator clip keeps a thermo-couple on nozzle very nicely

I don't think you need to get too fancy. You can switch to a plated copper block and nozzle with currently available parts, and that will behave similarly to moving the heater and sensor closer to the nozzle. Its possible that combining the nozzle and heat-block into a single component would make the nozzle respond even faster, but that comes with major disadvantages.

If you tune your PID with fans turned on or even while extruding it will hold temperature in use. You could also program software feed-forward since the printer knows how much filament is being melted at all times (and should therefore be able to calculate the theoretical required energy input, only relying on the sensor to deal with slower drift).

Firstly, 691175002 said "plated copper block and nozzle" from which I assume a block and nozzle made of copper and plated perhaps with nickle to stop it becoming oxidized, secondly, even if the nozzle was steel and plated with copper the copper with a conductivity of 386 w/m K versus steel with a conductivity of 36 W/m K would contribute a substantial improvement.

Firstly, 691175002 said "plated copper block and nozzle" from which I assume a block and nozzle made of copper and plated perhaps with nickle to stop it becoming oxidized, secondly, even if the nozzle was steel and plated with copper the copper with a conductivity of 386 w/m K versus steel with a conductivity of 36 W/m K would contribute a substantial improvement.

Learn a tiny bit of physics to back up your certainty of knowledge.
Mike

If you Assume1 691175002 "plated copper block and nozzle" then you do know.

1Assume isn't only used to mean "accept as truth without checking"; it also means "take on the form of." It might be safer if one not assume.

It seems a bit rich for cozmicray, the master of using only one word when 10 are needed, to say that 691175002 should have stated "nickel plated copper block hotend" instead of the already clear "plated copper block and nozzle". Having said that, let's go to the more important point: cozmicray claims that ±10° is O.K.
My tests show that ±3°C is pretty awful with bands of shiny alternating with matt. ±1°C is better and of course ±0.001°C (or earlier ±0.0001°) are neither achievable nor even asked for by anybody.
The reason I know is that I made some nozzles with a female thread fitted onto a stainless steel tube but the stainless steel acted like a heat break and caused wild temperature swings. I measured the temperature in a pocket drilled in the side of the nozzle with a 0.25mm diameter thermocouple.

As to why I would do such a thing when perfectly good nozzles are cheaply available? I did it to look to see if the nozzle hole aligned with the filament hole, if the sharpness of the edge shown in the diagram was important (it needs to be radiused) and if the inside needs to be polished (it does, up to about 3 times the nozzle hole diameter). Having a female thread made it possible to look at the inside with a microscope - something almost impossible in the deep well on a nozzle with a male thread.

My twopence worth, I've got some tungsten nozzles [www.kickstarter.com] and they definitely transfer heat more effectively to the filament than brass, when I installed it prints were stringing and looking shinier than before, at the same indicated nozzle temp.

See the deltaprintr mini hotend [deltaprintr.com] which has a hole in the nozzle for the thermistor and a clever heat proof sock that holds it on. Works in this design as the heater block is cylindrical.

In the perhaps forlorn hope that cozmicray is here in his participant aspect rather than his troll aspect, and in the hope that this thread does not become completely negative.

As to the material, I was using black PLA - cheap black PLA that shows up surface defects like nothing else. This was by intent as I was looking for problems.

For the material and manufacturer: I have no idea, nor does it matter what the manufacturer's temperature tolerance is, only how that filament behaves with that hotend, not to mention print speeds, nozzle diameter, cooling etc.. If the hotend temperature is mid range for the plastic it is possible that there may be a better tolerance although I still doubt ±10°C which is a span of 20°C. If however you are working low on the range to get fine detail then temperature control is much more important.

cozmicray entered this discussion with a claim that:-

QuoteThe difference between filament temp in nozzle
and the temp at the thermistor is minuscule.

Which I have found not to be the case. He also cryptically said:-

QuoteSo you using a filament material that you
must control temp +- 0.0001 deg C?

I can't remember ever seeing anybody claim that that degree of precision is needed.

He was however completely right about the IR thermometer, even 12mm spot at 300mm will be about £200

In his next posting, cozmicray completely misrepresents a posting as talking about a copper plated hotend, an error that he has, albeit grudgingly, admitted to. I will skirt over his faux-pas regarding PhDs, the conductivity of a copper film etc..

On his last two points:-

The length of the melt zone is not likely to be a factor, this particular hotned had longitudinal ribs on the inside of the heated zone to facilitate heat transfer.

The hotend is insulated by a shell made of cuttlefish bone which has a lower thermal conductivity than polystyrene foam.

Found a good article that may show some temperature effects
on PLA, dramatic surface effects

He does state"I also destroyed one of these vases at the time to see if the temperature made any obvious differences to bonding strength. I could not find any difference while splitting and ripping the different temperature printed areas."

Quotecozmicray
Found a good article that may show some temperature effects
on PLA, dramatic surface effects

He does state"I also destroyed one of these vases at the time to see if the temperature made any obvious differences to bonding strength. I could not find any difference while splitting and ripping the different temperature printed areas."

All true and many other things e.g., in the nozzle shown earlier it was actually made worse by the relatively good thermal conductivity of the brass nozzle, had it been a stainless steel nozzle the swings would have been much less.